1. Field of the Invention
The present invention relates to a peel-off-type sheet pack.
2. Description of the Related Art
A peel-off pack is a film-forming cosmetic material which is applied to skin, left for a certain period of time to form a film, and then peeled off the skin. Peel-off packs are known in a variety of configurations. With reference to FIG. 3, one of the types most popular because of its convenience is a sheet pack 10 having a multi-layer structure which is composed of a film-forming cosmetic material 4 and a moisture-permeable support 1 consisting of a hydrophilic layer 2 and a water repellent layer 3, wherein the film-forming cosmetic material 4 is supported on the hydrophilic layer 2, and a release sheet 5 is provided over the film-forming cosmetic material 4 as needed (Japanese Patent Application Laid-Open No. H11-12127).
When this sheet pack 10 is shaped to conform to a particular application site, such as the nose, it can be formed in a shape that will readily adhere to the site and afford a high manufacturing yield, as shown in FIG. 4A. When the sheet pack 10 is applied to the skin, it is applied as shown in FIG. 4B after the release sheet 5 is peeled off.
As to the materials from which the sheet pack 10 is formed, from standpoints such as cost and feeling, the hydrophilic layer 2 and the water repellent layer 3 are preferably formed from a hydrophilic nonwoven fabric and water repellent nonwoven fabric, respectively. A known method can be used to join the hydrophilic layer 2 and the water repellent layer 3 to form the moisture-permeable support 1, such as heat embossing, an air-through method, a hydroentangling method, needle punching, or spun bonding. In order to join securely the two layers so that they will not separate, the heat embossing, which can form local fused joints in the hydrophilic layer 2 and the water repellent layer 3, is a preferred method. To give a more specific example of how the moisture-permeable support 1 is manufactured, a mixed fiber layer of polypropylene fibers and rayon fibers is used as the hydrophilic layer 2 and laid over a polypropylene fiber layer that forms the water repellent layer 3, and these layers are joined by heat embossing to form a nonwoven fabric.
The moisture-permeable support 1 must have a certain amount of tensile strength in order to prevent the sheet pack 10 from tearing or leaving behind a sticky residue when the pack 10 is applied to the skin and then peeled away after the film-forming cosmetic material 4 has formed a film. However, in case that the nonwoven fabric that makes up the moisture-permeable support 1 is formed simply by heat embossing, hydroentangling or the like, the sheet pack 10 composed of the moisture-permeable support 1 with adequate tensile strength may not fit well against the external shape of the skin of an application site. In this case, it will be particularly difficult to closely apply the sheet pack 10 to places with three-dimensional shapes such as around the wings of the nose.
In light of the above problems associated with prior art, it is an object of the present invention to improve the fit of a sheet pack so that the pack can be easily applied to places such as the wings of the nose where conventional packs were difficult to apply.
The inventors found that the moisture-permeable support 1 of a conventional sheet pack 10 does not have a distinct yield point in its tensile characteristics, and consequently, upon receiving an increasing amount of tensile stress, the moisture-permeable support 1 breaks before undergoing sufficient plastic deformation, making it difficult for the pack to fit snugly against the skin. The inventors further found that an effective way of dealing with this is to use a moisture-permeable support in which there is a yield point in the tensile characteristics and in which the ratio between elongation at yield point and elongation at break is within a specific range.
Specifically, the present invention provides a sheet pack comprising a moisture-permeable support and a film-forming cosmetic material at least part of which is supported on the moisture-permeable support, wherein the moisture-permeable support has a yield point in its elongation-stress curve, the stress at the yield point is at least about 2 N/50 mm, and the elongation at yield point (%) divided by the elongation at break (%) is no more than about 0.8.
With the sheet pack of the present invention, the moisture-permeable support that serves as the support for the film-forming cosmetic material has a distinct yield point in its elongation-stress curve, and therefore the moisture-permeable support undergoes plastic deformation very quickly when the sheet pack is subjected to tensile stress above the yield point. Accordingly, it is possible to fit the sheet pack to a place on the skin with any three-dimensional shape by applying tensile stress to the sheet pack.
Furthermore, because the elongation at yield point (%) divided by the elongation at break (%) is no more than about 0.8 with the sheet pack of the present invention, when an increasing amount of tensile stress is applied, the sheet pack undergoes plastic deformation well before it breaks. This makes it possible to fit the sheet pack against the skin easily.